The present invention relates to an antifalsification paper having a security element in the form of a thread or band which consists of a transparent plastic film with an at least partly opaque coating and bears information in the form of visually and/or machine readable characters or patterns.
Bank notes and other monetary papers such as checks, shares, traveler's checks, check and credit cards, as well as passports and identity cards are frequently protected from forgery by the insertion or application of so-called safeguarding threads. Papers of this type will be referred to in the following as antifalsification papers. The safeguarding threads used for this purpose are made of a great variety of materials in the form of threads or bands with a width of 0.4 to 10 millimeters. They predominantly consist of plastic films which are metal-coated, printed, dyed or provided e.g. with pigment substances. Furthermore it is also known to give safeguarding threads magnetic, fluorescent, X-ray absorptive and other properties by selecting corresponding substances.
Metal-coated threads have recently been used increasingly for antifalsification papers. These threads, which are disposed partly or wholly within the paper, are almost invisible in incident light. This is because the light rays penetrating the upper paper layer are completely reflected on the metallic surface and scattered diffusely within the paper. In transmitted light, on the other hand, such threads appear as black stripes clearly standing out from their surroundings. Threads of this type cannot be imitated by a print on the paper. To increase the resistance to forgery it has also been proposed that such aluminized safeguarding threads be provided with microwriting (DE-A 14 46 851). However this has proved to be rather impractical since the writing is not recognizable on the otherwise opaque safeguarding thread in transmitted light and very difficult to recognize in incident light. Even when such safeguarding threads are incorporated in the paper as so-called window threads, as described in EP-C 0 059 056, the microprint remains difficult to find in the printed paper.
EP-A 0 279 880 discloses a safeguarding thread made of transparent film material on which metallically lustrous microcharacters are provided. The microcharacters are not recognizable in incident light since the thread is completely embedded within the bank note. In transmitted light, on the other hand, only the characters are recognizable since the safeguarding thread itself is of transparent design. The viewer thus sees in transmitted light only some writing running through the bank note that is difficult to find due to the smallness of the characters, their embedding in the paper stuff and a printed image possibly located thereabove. On the other hand, the small size of the microcharacters makes it difficult to imitate such a thread.
In a further safeguarding thread known from EP-A 0 330 733, a transparent plastic film, which can be colored, is provided with an all-over, opaque, in particular metallic, coating in which gaps in the form of characters or patterns are produced. The thread is recognizable in the document in transmitted light as a dark stripe, while the characters and patterns stand out in readily recognizable fashion as light, possibly colored surfaces from their immediate surroundings, the opaque thread coating, and additionally from their more removed surroundings, the document material. The thread is thus very easy to find in the document and the characters are also readable at any time without aid if they are large enough.
When such a thread is incorporated in an antifalsification paper as a window thread it offers additional copy protection in the area of the windows since the metallic luster of the coating cannot be reproduced by a copying machine and the copy therefore renders these areas in black.